Accident PZL M-18A Dromader N495WP,
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ASN Wikibase Occurrence # 294740
 
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Date:Monday 26 July 2004
Time:13:26 LT
Type:Silhouette image of generic M18 model; specific model in this crash may look slightly different    
PZL M-18A Dromader
Owner/operator:U.S. Forest Service
Registration: N495WP
MSN: 1Z0206
Total airframe hrs:3659 hours
Engine model:Pezetel ASZ621RM18
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Category:Accident
Location:Burns, OR -   United States of America
Phase: Unknown
Nature:Fire fighting
Departure airport:Burns Airport, OR (BNO/KBNO)
Destination airport:
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot was attempting to climb following a fire retardant drop. When he moved the throttle forward, the engine did not respond. The airplane started loosing altitude, and the pilot performed a forced landing to an open plateau. During the landing, the throttle would not retard all the way. In order to land the airplane, the pilot turned the fuel selector to the off position. During the landing roll, the left wing impacted a fence pole bending ribs and wrinkling the aileron. Post accident examination revealed that the bolt normally connecting the throttle linkage clevis to the throttle arm was missing. The investigating team examined a sister aircraft from the same provider. They found that a nylon lock nut had been installed on the clevis bolt, and it was loose enough to be removed without the aid of any tools. The industry standard, found in FAA Advisory Circular AC43.13-1B, chapter 7, section 4, paragraph 7-64, states that nylon locking nuts should not be used with rotating components or assemblies. It further states that nylon and/or fiber nuts are highly susceptible to wear from repetitive use and from high heat applications.

Probable Cause: The improper installation of the throttle linkage clevis to the throttle control arm by unknown maintenance personnel. Contributing factors were the nylon lock nut separating from its' bolt, which permitted the throttle cable to disconnect from the throttle control arm, and the fence post.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: SEA04TA147
Status: Investigation completed
Duration: 3 months
Download report: Final report

Sources:

NTSB SEA04TA147

Revision history:

Date/timeContributorUpdates
12-Oct-2022 08:36 ASN Update Bot Added

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